intel/hasvk: assume() we don't get ISL_NUM_FORMATS

Because coverity

CID: 1559412
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27369>

src/intel/vulkan_hasvk/genX_pipeline.c

@@ -153,6 +153,7 @@ emit_vertex_input(struct anv_graphics_pipeline *pipeline,
                                                   vi->attributes[a].format,
                                                   VK_IMAGE_ASPECT_COLOR_BIT,
                                                   VK_IMAGE_TILING_LINEAR);
+      assume(format < ISL_NUM_FORMATS);
 
       uint32_t binding = vi->attributes[a].binding;
       assert(binding < MAX_VBS);